Finding the Fourth Proportional to 42,809.40, 64,190.76 and 13,221.72

Step by Step Solution

1. Step 1: Write the proportion equation
   42,809.40 : 64,190.76 = 13,221.72 : x
2. Step 2: Convert to fraction form
   42,809.40/64,190.76 = 13,221.72/x
3. Step 3: Cross multiply
   42,809.40x = 64,190.76 × 13,221.72
4. Step 4: Simplify right side
   42,809.40x = 848,712,255.31
5. Step 5: Solve for x
   x = 848,712,255.31/42,809.40
6. Step 6: Final answer
   x = 19,825.37